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WHAT IS A GLACIER?

A glacier is a year-round mass of ice that originates on land, usually having an area larger than one tenth of a square kilometer. Many experts believe that a glacier must show some type of movement; others believe that a glacier can show evidence of present or past movement. Glaciers appear on every continent except Australia (although glaciers were present there during the last Ice Age).

Arctic Glaciers

The largest glaciers are continental ice sheets, enormous masses (greater than 20,000 square miles) of ice found only in Antarctica and Greenland. These sheets contain vast quantities of fresh water. If the Greenland ice sheet melted, it would cause sea levels to rise some 20 feet all around the world. If the Antarctic ice sheet melted, sea levels would rise up to about 200 feet.

Alpine Glaciers

Alpine glaciers, also called mountain glaciers, are found throughout the world's high mountains. If a mountain glacier increases in size and begins to flow down valley, it is then referred to as a valley glacier.

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HOW DOES A GLACIER FORM?

A glacier is formed from compacted layers of snow. When new layers of snow fall, previous layers compress into ice.

When the ice extends into the ocean, the temperature of the water and even lunar tides can influence how the floating ice shelf, or “tongue,” which extends into the ocean, responds. The breakup of the Larsen B ice shelf in 2002 is an example of the abrupt changes that can occur.

http://www.nsidc.org/...

Glacier and ice stream movement is complex. Although glaciers are
solid ice, they are in constant motion. Some, such as Alaska’s
Columbia Glacier, are literally rivers of ice, flowing down
mountains and around valleys.

Many glaciers end at the sea, where chunks of ice break off, or calve, into
the water.

This meltwater lake was created by warm summer temperatures on the surface of the Greenland Ice Sheet. The water pooling on the surface of a glacier or ice sheet is heavier and denser than ice. It eventually flows into moulins, or stream channels, which drill their way down through the ice; the water then flows out the base of the glacier into the ocean. Meltwater lubricates the glacier bed and speeds up the flow of ice into the sea. Global warming has caused melting to occur dozens of miles further inland than 20 years ago.

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WHAT DO GLACIERS HAVE TO DO WITH GLOBAL WARMING?

Global Warming & Climate Change

Global warming is the increase in the average temperature of the Earth’s near-surface air and oceans since the mid-20th century and its projected continuation.

Global surface temperature increased 1.33ºF (+/- 0.32 °F) between 1905 and 2005 and is projected to rise 1.8ºF to 2.7ºF by 2050. (Since global temperature recording began in 1850, the ten hottest years on record, in order from hottest to less hot, have been: 2005, 1998, 2002, 2003, 2007, 2006, 2004, 2001, 1997 and 1995.) The Intergovernmental Panel on Climate Change (IPCC) concludes that most of the temperature increase since the mid-20th century is “very likely” due to the increase in anthropogenic (meaning manmade) greenhouse gas concentrations. Natural phenomena such as solar variation and volcanoes probably had a small warming effect from pre-industrial times to 1950 and a small cooling effect from 1950 onward. These basic conclusions have been endorsed by at least 30 scientific societies and academies of science, including all of the national academies of science of the major industrialized countries.

Reports on climate change can be found at:
http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_SPM.pdf
http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_Ch09.pdf

The terms “global warming” and “climate change” are often used interchangeably.

Why Do Glaciers Matter?

Ice that took centuries to develop can vanish in just a few years. A glacier doesn’t melt slowly and steadily like an ice cube on a table. Once glacial ice begins to break down, the interaction of meltwater and sea water with the glacier’s structure can cause increasingly fast melting and retreat. Today, Earth’s surface is made up of 71% water, 10% ice, and 19% land. Most of the world’s ice is in the Arctic and Antarctic, but some of it is scattered around Earth in the form of mountain glaciers.

Glaciers are sentinels of climate change. They are the most visible evidence of global warming today. In addition to raising sea water levels, widespread loss of glaciers will likely alter climate patterns in other, complex ways. For example, glaciers’ white surfaces reflect the sun’s rays, helping to keep our current climate mild. When glaciers melt, darker exposed surfaces absorb and release heat, raising temperatures. Our way of life is based on climate as we know it.

Could This Be a Natural Cycle?

Throughout Earth’s history, ice caps and glaciers have grown and melted in response to changes in the Earth’s energy balance. Now, however, the addition of atmospheric greenhouse gases, including carbon dioxide (CO2), methane (CH4), and manmade gases such as nitrogen trifluoride (NF3), is amplifying the natural greenhouse effect, causing intensified warming that international teams of scientists describe as unequivocal, meaning “without doubt.”

In normal circumstances—without human activities influencing the climate and amplifying the greenhouse effect—glaciers and ice caps melt in the summer months, and in the high latitudes when the sun doesn’t set for weeks at a time around the solstice, the melt can be dramatic. [0]

Glaciers that terminate at an ocean also tend to break off—or calve—icebergs faster in summer, causing a seasonal retreat. In the winter months, especially in high latitudes when the sun doesn’t come above the horizon for weeks at a time, the ice grows. On the Greenland ice cap, for instance, there is tremendous melting during the summer, especially on the edges where glaciers meet the sea, but there is also buildup of ice and snow from precipitation during the winter months.

Ocean-ending glaciers slow down their rate of calving in the winter months and recover some or all of their summertime loss. The difference between the summer loss and the winter growth is studied by examining the “mass balance.” Most glaciers in the world have a negative balance and are retreating, and the few that are advancing appear to be close to equilibrium.

What alarms many scientists is not only the extent of retreat but the rapidity of the change and the consistent, worldwide emergence of retreat and volume loss. The EIS time-lapse studies provide evidence not only of the changes that are occurring, but of the processes involved, which have not been well understood.

Glaciers and ice caps are indeed key indicators and unique demonstration objects of ongoing climate change. Their shrinkage and, in many cases, even complete disappearance leaves no doubt about the fact that the climate is changing at a global scale and at a fast if not accelerating rate. Anyone can see the changes in glacier extent and understand the basic physical principle of snow and ice melting as temperatures continue to rise: as the glaciers and ice caps on earth grow smaller, the energy content in the climate system and in the environment on which we depend becomes greater.

The average annual melting rate of mountain glaciers appears to have doubled after the turn of the millennium in comparison with the already accelerated melting rates observed in the two decades before. The previous record loss in the year 1998 has already been exceeded three times, i.e., in the years 2003, 2004 and 2006, with the losses in 2004 and 2006 being almost twice as high as the previous 1998 record loss.
—Wilfried Haeberli, Director, World Glacier Monitoring Service

Why Didn’t Scientists Recognize Global Warming Sooner?

Some did. In 1958, the National Academy of Sciences published a booklet titled “Planet Earth: The Mystery with 100,000 Clues,” which contained this prescient paragraph:

Our industrial civilization has been pouring carbon dioxide into the atmosphere at a great rate. By the year 2000 we will have added 70 percent more carbon dioxide to the atmosphere. If it remained, it would have a marked warming effect on the earth’s climate, but most of it would probably be absorbed by the oceans. Conceivably, however, it could cause significant melting of the great icecaps and raise sea levels in time.

[PHOTO CREDIT http://www7.nationalacademies.org/archives/IGYPlanetEarthPosters.html]

When the authors wrote about the natural greenhouse effect that allows life on Earth to exist and pointed to the potential impact of human activities—specifically adding carbon dioxide to the atmosphere by burning fossil fuels—they knew a good deal about the Earth’s energy balance. They also knew enough about the role of greenhouse gases such as carbon dioxide in trapping heat radiated from the Earth’s surface to predict the potential future melting of ice caps and raised sea levels. But they were off on several key points. It would have been difficult to imagine the population of the planet more than doubling, and the demand for fossil fuel energy growing exponentially[0].

In fact, by the year 2000, the release of global fossil carbon emissions into the atmosphere went from around 2,000 million metric tons to more than 6,000 million metric tons of carbon, and now it is around 8,000 million metric tons, or 30,000 million metric tons of CO2. Moreover, the authors of “Planet Earth” anticipated the ocean would absorb most of the carbon dioxide when in fact it currently absorbs only about 30%, which is causing changes in the chemistry of the water that are acidifying the ocean.

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GLOSSARY

An excellent, comprehensive glossary of terms related to glaciers can be found at the National Snow and Ice Data Center website, http://nsidc.org/glaciers.

Glacier
A mass of ice that forms on land when more snow falls than melts each year

Ice Cap
A dome-shaped mass of glacier ice that spreads out in all directions; an ice cap is larger than an icefield but less than 50,000 square kilometers

Ice Sheet
A dome-shaped mass of glacier ice that covers surrounding terrain and is greater than 50,000 square kilometers, i.e., the Greenland and Antarctic ice sheets

Ice Shelf
Ice that has pushed out over the ocean but is still attached to a land-based ice mass

Iceberg
Piece of ice that breaks off from a glacier, ice cap, or ice shelf and floats in the water

Icefield
A mass of glacier ice; similar to an ice cap and usually smaller and lacking a domelike shape; somewhat controlled by terrain

Sea Ice
Ice, formed of frozen sea water, floating on an ocean

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ADDITIONAL RESOURCES

World View of Global Warming
Glaciers and Glacial Warming, Receding Glaciers
http://www.worldviewofglobalwarming.org/pages/glaciers.html

Retreat of Glaciers since 1850
http://en.wikipedia.org/wiki/Retreat_of_glaciers_since_1850

Double Exposure—Photographs of Climate Change
http://doublexposure.net/index.html

NSIDC Glaciers Repeat Photography
http://nsidc.org/data/glacier_photo/repeat_photography.html

All About Glaciers
http://nsidc.org/glaciers/

Glaciers Online
http://www.swisseduc.ch/glaciers/

Center for Remote Sensing of Ice Sheets
https://www.cresis.ku.edu/

Intergovernmental Panel on Climate Change
http://www.ipcc.ch/index.htm

British Antarctic Survey
http://www.antarctica.ac.uk/bas_research/our_views/index.php

FAQ—16-page overview of climate change science with a focus on ice sheets from CReSIS at the University of Kansas (~9 MB PDF) https://www.cresis.ku.edu/news/documents/ClimateChangeFAQ.pdf

The World Glacier Monitoring Service (WGMS) is the collaboration of several high-level international organizations including the United Nations Environmental Programme and the World Meteorological Organization:
http://www.wgms.ch/

United Nations Environmental Programme 2008 report “Global Glacier Changes: Facts and Figures” provides an overview of the status of glaciers around the world:
http://www.grid.unep.ch/glaciers/

K-12 teachers participate in polar research, working closely with scientists as a pathway to improving science education.
http://www.polartrec.org/


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RESOURCES FOR TEACHERS

Grades K–2 A Vacation to the Polar Regions
Students will learn about the characteristics of the Arctic and Antarctic by looking at a globe and at pictures of the polar landscape and animals. They will plan a vacation to one of these regions and draw pictures or write stories depicting themselves on the trip.
http://www.nationalgeographic.com/xpeditions/lessons/05/gk2/polar.html

Grades 3–5 Expedition to the Poles
Students will pretend they have just returned from a year in the Arctic or Antarctic. They will look at websites about these regions and expeditions to them, and they will create posters illustrating their experiences. Students will conclude by writing paragraphs explaining what it would be like to visit the polar region that they did not focus on in this lesson.
http://www.nationalgeographic.com/xpeditions/lessons/05/g35/expedition.html

Grades 3–5 What's Happening to the Emperor Penguins?
Students will learn about emperor penguins’ habitat and behaviors through websites such as National Geographic Creature Feature: Emperor Penguins and will illustrate a map to show what they have learned. They will view pictures of icebergs that are affecting penguin colonies and consider what impacts these icebergs might have on the penguins. They will conclude by writing paragraphs describing the maps that they have illustrated.
http://www.nationalgeographic.com/xpeditions/lessons/18/g35/seaspenguin.html

Grades 3–5 Antarctica: A Cold Desert Ecosystem
In this lesson students will construct a rough map of Antarctic ecosystems and explore relationships among the creatures that populate them. [Note: This lesson can be adapted to focus on other regions, including the one in which you live.]
http://www.nationalgeographic.com/xpeditions/lessons/08/g35/antarctica.html

Grades 6–8 What Do People Know about the Arctic and the Antarctic?
In this lesson, students will research the landscapes, climates, and animal life of the polar regions and learn the differences between the Arctic and the Antarctic.
http://www.nationalgeographic.com/xpeditions/lessons/05/g68/knowabout.html

Grades 6–8 To the Ends of the Earth: Research in Polar Seas
In this lesson students will learn about famous explorers of the polar regions and have a simulated polar exploration of their own.
http://www.nationalgeographic.com/xpeditions/lessons/01/g68/earth.html

Grades 6–8 Icebergs and Penguins
Students will read the National Geographic News article “Ice Buildup Hampers Penguin Breeding in Antarctica” to learn about the problems caused by these icebergs. They will
see photographs of icebergs moving over time and write brief papers pretending to be scientists reporting on the status of emperor penguin populations.
http://www.nationalgeographic.com/xpeditions/lessons/18/g68/seaspenguin.html

Grades 9–12 Environmental Issues in the Polar Regions
Students will learn about how environmental problems affect the polar regions, and they will create magazine ads to educate the public about these problems and to convince people to pay more attention to human impacts on the Arctic and Antarctic.
http://www.nationalgeographic.com/xpeditions/lessons/05/g912/polarregions.html

Grades 9–12 Climate and CO2: Analyzing Their Relationship
In this lesson, students will speculate on various scenarios of future world climates if the greenhouse effect increases.
http://www.nationalgeographic.com/xpeditions/lessons/07/g912/co2.html

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